This invention relates to a method and apparatus for controlling an apparatus for texturizing multifilament yarn made of synthetic polymeric materials wherein the filaments of the yarn are pneumatically conveyed into a bulking chamber to form a compacted yarn mass and in particular, to a method and apparatus for controlling startup and shutdown of the apparatus as well as monitoring of faults in the bulking procedure during continuous operation.
Heretofore, many processes and apparatus have been developed for texturizing yarn made of thermoplastic polymeric materials by the employment of fluid jets or the like pneumatic means. Many of these prior developments have been relatively successful in providing bulky voluminous yarn having a degree of crimp uniformity and improved dyeing characteristics suitable for use in the production of textile fabrics, carpets and the like. The apparatus employed for carrying out these known processes is complex and often requires elaborate control systems to regulate the operation of the apparatus, especially during startup and shutdown.
Because of the advantages found in these pneumatic processes for producing texturized yarns, particularly the high yarn processing speeds, the need for such control systems for operating the apparatus have been accepted by the textile industry.
In the known processes for bulking yarn pneumatically, an initially straight and pre-drawn yarn which may be untwisted or slightly twisted is subjected to a turbulent heated fluid such as steam in such a manner that the individual filaments of the yarn are looped, coiled or crimped and the yarn is heat-set in this condition. The individual filaments are in this manner formed into a bulky wool-like product wherein each of the filaments in a relaxed condition exhibit a plurality of crimps or loops along a given length. Such crimps are usually offset and out of phase with each other in a random manner.
In order to ensure the provision of uniform crimps, bulking chambers are often employed to receive yarn from an aspirator jet to cause the formation of a compact mass of yarn or yarn plug which is continuously pushed or otherwise removed from the bulking chamber.
U.S. Pat. No. 3,373,470 describes a process for a stuffer-type crimping of thermoplastic filaments wherein the filaments are introduced into one end of an elongated confined space or bulking chamber by a stream of fluid such as steam under pressure and at a temperature sufficient to set the filaments. The filaments are tightly packed within the confined space by controllably releasing part of the fluid from the confined space laterally of the confined space at a position spaced from the other end and the packed filaments are then forced through the space to the other end under pressure by the remaining portion of fluid which exhausts with the yarn. The confined space required for this process is defined by a metal spring having gaps between the convolutions thereof. In this apparatus, the yarn is propelled by the action of the fluid from a nozzle through a tubular passage and then into the interior of the spring. The spring is curved to a desired extent to obtain optimum compacting of the yarn therein.
Additional apparatus and processes for texturizing synthetic yarns pneumatically are disclosed in U.S. Pat. Nos. 3,343,240 and 3,576,058. In the processes disclosed in each of these patents, steam is discloded as being a suitable fluid for conveying the filaments of the yarn into a zone wherein the yarn undergoes compression. An especially effective process and apparatus for texturizing yarns by aspirating the yarn into a bulking chamber is also described in the application of Brewster Eskridge, et al executed on even date herewith (Ser. No. 517,802, Oct. 24, 1974.).
During the start-up of such processes, the thermoplastic yarn may become overheated by the heated gas and consequently, the filaments of the yarn may become fused together or become sufficiently tacky to stick to each other and thereby cause plugging of the bulking chamber or other zone wherein the yarn is compacted. Also, during emergency stoppage of the apparatus due to a yarn breakage or the like breakdowns or during scheduled shutdown of the apparatus, the yarn again may become overheated by the steam and/or the heat retained in the apparatus and consequently there is a risk of the yarn again plugging the apparatus.